High precision hollow conductor structure for the transmission of electromagnetic waves, and method of making the same

ABSTRACT

A high precision hollow conductor structure, and method of making same, for the transmission of electromagnetic waves, such as H01 type waves, in which a hollow conductor member forming the inner wall of the conductor structure is constructed with high accuracy by electro-formation on a mandrel, the conductor member having an inner diameter of circular configuration with the inner surface being uniform within very low tolerances, whereby, efficient wave transmission therein may be achieved, a metal jacket, having an undulating longitudinal cross-section, encircling said conductor member in rigid relation with respect thereto, with the interstices between the member and the jacket being filled with a rigid material, the matrix core being removed from said hollow conductor member following assembly of said member and jacket.

llnited States Patent [191 Larsen et al.

Assignees: Siemens Aktiengesellscliatt, Berlin;

Kabel-und Metallwerlre Guteholffnung-shutte Aktiengesellschallt, Hanover, Germany Filed: Mar. 13, 1970 Appl. No: 24,405

Related US. Application Data Division of Ser. No. 771,253, Oct. 28, 1968.

US. Cl ..29/600, 29/447 Int. Cl. ..H0lp ill/00, B23p 11/02 Field of Search ..333/97, 95; 29/600, 29/601, 447; 204/9 References Cited UNITED STATES PATENTS 11/1969 Martin ..29/600 UX 1/1970 Dugan et a1. ..29/600 Reproduction of or Written Disclosure of British Pat. 4,499 issued April 11, 1895, Inventor Ekmore, 2 pages.

Fialkoff ..204/9 Primary Examiner-Charles W. Lanham Assistant Examiner-R. M. Rogers Attorney-Hill, Sherman, Meroni, Gross & Simpson [57] ABSTRACT A high precision hollow conductor structure, and method of making same, for the transmission of electromagnetic waves, such as l-I type waves, in which a hollow conductor member forming the inner wall of the conductor structure is constructed with high accuracy by electro-formation on a mandrel, the conductor member having an inner diameter of circular configuration with the inner surface being uniform within very low tolerances, whereby, efficient wave transmission therein may be achieved, a metal jacket, having an undulating longitudinal cross-section, encircling said conductor member in rigid relation with respect thereto, with the interstices between the member and the jacket being filled with a rigid material, the matrix core being removed from said hollow conductor member following assembly of said member and jacket.

4 Claims, 2 Drawing Figures 1 men PRECISION HOLLOW CONOUCTOR STRUCTURE FOR THE TRANSMISSION OE ELECTROMAGNETIC WAVES, AND METHOD OE MAKING THE SAME CROSS REFERENCE TO RELATED APPLICATION This application is a Division of my pending Application Ser. No. 771,253 filed Oct. 28, 1968.

BACKGROUND OF THE INVENTION The invention is directed generally to a hollow conductor structure for the transmission of electromagnetic waves, and more particularly to the production of a hollow conductor structure having a precise circular cross-section, operable to efficiently transmit signals or large quantities of energy in the form of microwave energy over relatively long distances, with the hollow conductor structure being capable of disposition in the ground without detrimental effects on the precise geometrical dimensions thereof. These specifications require a wave conducting structure possessing a high degree of precision in its circular cross-section and an axis as straight as possible, as well as possessing adequate structural reenforcement to insure maintenance of the necessary stability of tolerances when the structure is subjected to influences resulting from the disposition thereof underground.

The transmission of electromagnetic hollow waves, particularly of the H wave type, as is known, requires as rectilinear a placement of the hollow conductors as possible. In one arrangement of the prior art, undesired curvature of the hollow conductor is reduced to a minimum and thus ineffective construction-wise insofar as the dissemination of the wave is concerned, by floating the hollow conductor within a protective tube, the liquid medium being oil, and the hollow conductor lying on base members, ties, or the like which are rectilinearly disposed, the conductor contacting such base members with a slight play and without the application of undue pressure on the conductor.

In another conduit structure of the prior art, hollow conductors were inserted into protective tubes or pipes of steel to provide adequate mechanical strength and adequate resistance against corrosion of the electromagnetic hollow conductor, which was preferably made of copper or aluminum and thus could not effectively be placed directly into the ground. In a further known conduit structure, the hollow conductors are disposed within a protective tube or pipe of sufficient diameter that a free space exists between the outer wall of the hollow conductor and the inner wall of the protective tube or pipe with such space extending over the entire circumference. Such space may then be filled with a plastic sealing compound preferably bitumen, and if a plurality of hollow conductors are employed within such protective pipe, the space therebetween is filled in like manner.

However, it has been ascertained that if the theoretically possible low attenuation values for transmission of electromagnetic energy by means of the H wave are to be attained, very high precision must be employed with respect to the cross-section and surface quality of the inner hollow conductor wall, as well as the straightness of the axis thereof. The problem to be solved thus is to meet these requirements in an economically practical manner.

SUMMARY OF THE INVENTION This problem is solved, in accordance with the invention, by the utilization of hollow conductors of circular cross-section, produced by electroforming and embedded in a metal jacket having an undulating longitudinal cross-section. The hollow conductor member may be advantageously produced as an electroformed reproduction with the interstices between the hollow conductor and the metal jacket being filled by a hardenable synthetic resin. The inner surface of the hollow conductors may be covered with a thin layer of a suitable dielectric material in accordance with known techniques.

The hollow conductor for the electromagnetic waves is produced according to the invention electroconductively preferably by electroformation on a circularly ground mandrel of a length to accommodate the desired production length of the conductor, for example several meters. The wall thickness of the hollow conductor thus produced may be maintained at a comparatively low figure, for example in geometric dimensions as precisely as the size range of one millimeter, resulting in a considerable savings in cost. Electroreproduction may be defined as the production of copies of an item by electroforming techniques and in the present instance, a mandrel or core is employed, preferably a steel pipe or tube which in accordance with known techniques can be produced with very great precision. Thus the core can be provided with a precisely circular cross-section extending along a precisely straight axis. As such surface determines the quality of the inner surface of the hollow conductor, such inner surface thus can be produced in all of its geometric diemnsions as precisely as the outer surface of the core on which it is formed.

A conductor so produced, due to its thin walled construction, possesses insufficient inherent stiffness to permit its employment as a unitary structure, far less placed under ground. This structure, however, does answer the first requirement involved, namely of providing a hollow conductor having the qualities necessary for efficient transmission of the electromagnetic waves, and the remaining problem consequently is to impart to such conductor adequate mechanical reinforcements I to ultimately produce a conductor structure, retaining the desired transmission characteristics and at the same time having sufficient mechanical strength to undergo even high mechanical stresses. The desired results are accomplished by inserting the thin walled hollow conductor thus produced into a suitable metal jacket having an undulating longitudinal cross-section with the interstices between the conductor and the jacket being filled by suitable hardenable synthetic resin.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings wherein like reference characters indicate like or corresponding parts;

FIG. 1 is a longitudinal sectional view, on an enlarged scale through a conductor structure in accordance with the invention; and

FIG. 2 is a similar view illustrating details in the production thereof.

DETAILED DESCRIPTION THE INVENTION Referring to the drawings and more particularly to FIG. l the reference numeral 1 designates a hollow conductor which is electroformed from copper and is disposed within a generally tubular shaped jacket 2 preferably of steel which, as illustrated and formed with an undulating longitudinal cross-section, the inner diameter of the jacket 2 being illustrated as being outwardly spaced from the periphery of the hollow conductor 1. The intervening space between the hollow conductor 1 and the metal jacket 2 is filled with a suitable age-hardening plastic or synthetic resin 3, which as illustrated also fills the interstices formed by the undulating configuration of the jacket.

While this structure may be adequate for specific applications, it may be desirable to further increase the longitudinal rigidity of the conductor structure by disposing the assembly thus far described into a smooth walled tubular conduit 5, which in the embodiment illustrated is disposed in firm contacting engagement with the undulations of the jacket 2. If desired, the interstices between the member 5 and the undulations of the member 2 may likewise be filled with suitable material, for example, a synthetic resin similar to the material 3, and in the event it is desired to employ a member 5 of greater diameter, the material 6 may also be utilized as the connecting means between the jacket 2 and the member 5. Additional protection for the outer member 5 may likewise be provided, for example in the form of a suitable protective jacket 7 constructed, for example, of polyethylene or other suitable material. Likewise, in the event that no reinforcing member 5 or cooperable material 6 is required, the plastic jacket 7 may be applied directly upon the metal jacket 2.

In the fabrication of the structure illustrated in FIG. 1, as illustrated in F IG. 2, the hollow conductor ll may be produced upon a suitable mandrel 8 which has an external diameter corresponding to the desired internal diameter of the conductor to be formed thereon and of a length to accommodate the desired length of the finished conductor. As previously mentioned, the mandrel 8 may be readily and economically produced with an extremely high degree of accuracy with respect to the circular periphery, the smoothness and finish of the outer surface thereof and the axial straightness of the mandrel. The mandrel 8 is then employed as the matrix or core for the hollow conductor to be formed, with the metal, i.e., copper being electrodeposited thereupon whereby the inner surface of the hollow conductor 1 will closely correspond to the exterior surface of the mandrel with respect to accuracy, finish, etc., and the high precision employed in the production of the mandrel is thus reflected in the character of the inner surface of the finished hollow conductor.

Upon completion of the formation of the conductor 1, and while it is still supported on the mandrel 8, it is inserted in the metal jacket 2, with the intervening spaces and interstices therebetween being filled with the synthetic resin 3. Following hardening of such resins, which for example, may be accelerated by chilling, the mandrel 8 may then be suitably chilled, for example by passing a cooling fluid there-through, and then withdrawn from the conductor 1. The undulations or corrugations in the metal jacket 2 may be formed at a suitable step in the construction, such undulations being formed prior to the insertions of the hollow conductor therein, or after assembly, in accordance with known techniques.

In the event that the conductor structure, thus far described, is to be further reinforced, the elements 5, 6 and 7 may be applied thereto in suitable sequence.

It will be appreciated that the above described construction results in the highly desirable combination of a hollow conductor which can be produced with a very high precision heretofore unattainable, and with excellent protection from mechanical stresses. Likewise, due to the novel arrangement, including the use of a corrugated or undulated reinforcing member, an unusually high transverse rigidity is achieved at a relatively low material expenditure.

Having thus described our invention it will be apparent from the above disclosure that various and material modifications may be made in the same without departing from the spirit and scope of our invention.

We claim as our invention:

1. A method of forming a hollow conductor structure for the transmission of electromagnetic waves, such as H type waves, comprising the steps of: circularly grinding an elongate cylindrical mandrel to a diameter of very low tolerance corresponding to the desired inner diameter of the conductor to be formed and having a length to accommodate the desired length of the conductor to be formed, electro-forming on the mandrel a layer of metal to form the inner wall of the hollow conductor structure, disposing the mandrel carrying the layer of metal in an outer tubular jacket of undulating longitudinal cross-section, filling the interstices between the outer jacket and the layer of metal with a plastic which can harden, and, following hardening of the plastic, shrinking and removing the mandrel.

2. A method of forming a hollow conductor structure for the transmission of electromagnetic waves, such as H type waves, comprising the steps of: circularly grinding an elongate hollow cylindrical mandrel to a diameter of very low tolerance corresponding to the desired inner diameter of the conductor to be formed and having a length to accommodate the desired length of the conductor to be formed, electroforming on the mandrel a layer of metal to form the inner wall of the hollow conductor structure, disposing the mandrel carrying the layer of metal in an outer tubular jacket of undulating longitudinal cross-section, filling the interstices between the outer jacket and the layer of metal with a plastic which can harden, and, following hardening of the plastic passing a chilling fluid through the mandrel to shrink the mandrel and removing the mandrel.

3. A method of forming a hollow conductor structure for the transmission of electromagnetic waves, such as H type waves, comprising the steps of: circularly grinding an elongate hollow cylindrical mandrel to a diameter of very low tolerance corresponding to the desired inner diameter of the conductor to be formed and having a length to accommodate the desired length of the conductor to be formed, electroforming on the mandrel a layer of copper to form the inner wall of the hollow conductor structure, disposing the mandrel carrying the layer of copper in an outer tubular steel jacket of undulating longitudinal cross-section, filling the interstices between the outer jacket and the layer of copper with a plastic which can harden, and, following hardening of the plastic passing a chilling fluid through the mandrel to shrink the mandrel and removing the mandrel.

4. A method of forming a hollow conductor structure for the transmission of electromagnetic waves, such as H type waves, comprising the steps of: machining an elongate mandrel to a dimension of very low tolerance to form the inner wall of the hollow conductor structure, disposing the mandrel carrying the layer of metal in an outer tubular jacket of undulating longitudinal cross-section, filling the interstices between the outer corresponding to the desired inner dimension of the 5 jacket and the layer of metal with a plastic which can conductor to be formed and having a length to accommodate the desired length of the conductor to be formed, electroforming on the mandrel a layer of metal ing and removing the mandrel. 

1. A method of forming a hollow conductor structure for the transmission of electromagnetic waves, such as H01 type waves, comprising the steps of: circularly grinding an elongate cylindrical mandrel to a diameter of very low tolerance corresponding to the desired inner diameter of the conductor to be formed and having a length to accommodate the desired length of the conductor to be formed, electro-forming on the mandrel a layer of metal to form the inner wall of the hollow conductor structure, disposing the mandrel carrying the layer of metal in an outer tubular jacket of undulating longitudinal cross-section, filling the interstices between the outer jacket and the layer of metal with a plastic which can harden, and, following hardening of the plastic, shrinking and removing the mandrel.
 2. A method of forming a hollow conductor structure for the transmission of electromagnetic waves, such as H01 type waves, comprising the steps of: circularly grinding an elongate hollow cylindrical mandrel to a diameter of very low tolerance corresponding to the desired inner diameter of the conductor to be formed and having a length to accommodate the desired length of the conductor to be formed, electroforming on the mandrel a layer of metal to form the inner wall of the hollow conductor structure, disposing the mandrel carrying the layer of metal in an outer tubular jacket of undulating longitudinal cross-section, filling the interstices between the outer jacket and the layer of metal with a plastic which can harden, and, following hardening of the plastic passing a chilling fluid through the mandrel to shrink the mandrel and removing the mandrel.
 3. A method of forming a hollow conductor structure for the transmission of electromagnetic waves, such as H01 type waves, comprising the steps of: circularly grinding an elongate hollow cylindrical mandrel to a diameter of very low tolerance corresponding to the desired inner diameter of the conductor to be formed and having a length to accommodate the desired length of the conductor to be formed, electroforming on the mandrel a layer of copper to form the inner wall of the hollow conductor structure, disposing the mandrel carrying the layer of copper in an outer tubular steel jacket of undulating longitudinal cross-section, filling the interstices between the outer jacket and the layer of copper with a plastic which can harden, and, following hardening of the plastic passing a chilling fluid through the mandrel to shrink the mandrel and removing the mandrel.
 4. A method of forming a hollow conductor structure for the transmission of electromagnetic waves, such as H01 type waves, comprising the steps of: machining an elongate mandrel to a dimension of very low tolerance corresponding to the desired inner dimension of the conductor to be formed and having a length to accommodate the desired length of the conductor to be formed, electroforming on the mandrel a layer of metal to form the inner wall of the hollow conductor structure, disposing the mandrel carrying the layer of metal in an outer tubular jacket of undulating longitudinal cross-section, filling the interstices between the outer jacket and the layer of metal with a plastic which can harden, and, following hardening of the plastic, shrinking and removing the mandrel. 